bug#68948: highlight error, cannot open filetypes.conf: No such file or directory

[chris]

Below changes at the highlight package resolve the issue here but may adversely 
affect "highlight-gui" functionality. Will wait for 
https://issues.guix.gnu.org/70047 before trying to proceed,
```diff
-      #:make-flags #~(let ((confdir (string-append %output
-                                                   
"/share/highlight/config/")))
-                       (list (string-append "PREFIX=" %output)
-                             (string-append "HL_CONFIG_DIR=" confdir)
-                             (string-append "conf_dir=" confdir)))
+      #:make-flags #~(list (string-append "PREFIX=" %output)
+                           (string-append "HL_CONFIG_DIR=" %output "/etc/")
+                           (string-append "conf_dir=" %output "/etc/"))
```